Ever since the accessibility of modern medicine inc reased all over the world, the rampant and misuse also increase considerably. A continuous res earch resulting in introduction of the newer compounds is going on. Many of these are being intr oduced and used without complete of drugs. The pharmacist because of different reasons is unab le to practice the rational drug therapy that is supply right drug, at right time in right dose to t he patient. The present article takes the help of some published reports to explain irrational or mis use of drug leading to fatal effect. The article also highlights the major reasons involved in the i rrational use of drugs. Not only the irrational use but the drugs having the adverse reaction and h azardous effects are also used in large amount in developing nations due regulatory reasons. The u se of these drugs without the complete knowledge has also a major problem. In this article the author has given emphasis on the drug hazards and rational use of drug by giving some rep orts like US FDA, different hazardous effect of drug. Author has also explained the rational use of drug in terms of medical, socio economic and some legal aspects along with reasons for irrat ional use of drug and obstacles exist in rational drugs, also includes some steps to improve rational drug prescribing method, and conclude that drug may act as a God or may act as a Devil if not used properly.